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Relaxed Delegates

Sun, August 12, 2007, 10:53 AM under Orcas | VisualStudio
I knew about covariance and contravariance that we got in the .NET 2.0 timeframe and I also knew that VB 9.0 (shipping with Visual Studio 2008) would fully support the feature and even enhance it. I hadn't appreciated how much it would be enhanced until I accidentally run into it yesterday (while recording a video on VB intellisense improvements).

I created a thread and had the delegate point to a method that I had already written. So I went to change my method to accept the Object as an argument and before having a chance I noticed that VB's background compiler hadn't complained about it!? In case you haven't guessed it by now, in VB9 you can omit the parameter list of a method pointed by a delegate, if you wish ;-)

Example:
' No need to type (s As Object, e As EventArgs)
Sub Button1_Click() Handles Button1.Click    
    Dim t = New Thread(AddressOf MyWorkerMethod)
    t.Start()
End Sub

Sub MyWorkerMethod() 'No need to type (o As Object)
    'Do sth on worker thread
End Sub

Read more about relaxed delegates on msdn (bottom of the article). Like with all other language features, you can use this one in your .NET 2.0 projects in VS 2008.
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